Insulated coil for electric apparatus



, INSULATED COIL FOR ELECTRIC APPARATUS Filed Dec. 18, 1944 .Figi.

' Inventor: Hehm an Britt en,

6' by zVa/wy His Attorneg.

Patented Nov. 29, 1949 INSULATED COIL FOR ELECTRIC APPARATUS Herman Britten, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 18, 1944, Serial No. 568,759

6 Claims. 1 My invention relates to electrically insulated coils for electric apparatus, more particularly to blowout coils for electromagnetically operated switches known as contactors, and has for its object a compact, reliable and low cost electric insulation for the turns of the coil whereby the turns may be secured tightly together thereby to shorten the coil.

My invention is especially applicable to the electric insulation of the turns of a coil made from a strip conductor wound edgewise into a helix. In accordance with my invention, the electric insulation for the turns of the coil is applied after the coil has been wound.

In carrying out my invention in one form, I utilize a strip of crepe paper, i. e., paper which is crimped or corrugated, the strip of paper being cut crosswise of the corrugations. Before application to the conductor, the strip of paper is folded lengthwise somewhat on one side of its middle. It is applied to the edgewise wound helical conductor with the side portions on opposite sides of the conductor and the junction or fold on the outer peripheral edge of the conductor. During the application of the paper to the coil, a suitable tension is applied to it along the bend or fold so that the paper is stretched and the side portions fit substantially fiatwise against the opposite sides of the strip conductor. Thereafter, the turns are bound tightly together and the coil impregnated with a suitable electrically insulating material, such as varnish.

For a more completeunderstanding of my invention, reference should be had to the accompanying drawing, Fig. 1 of which is a fragmentary elevation view of apparatus for applying the crepe paper to the coil and showing the paper being applied; Fig. 2 is an enlarged sectional view of the folded strip of crepe paper; Fig. 3 is an enlarged sectional view of a strip conductor of the coil with the paper insulation applied; while Fig. 4 is a side view of a completed coil.

Referring to the drawing, for the convenient application of the folded strip of crepe paper I to the edgewise wound strip conductor 2, I provide a mandrel 3 which extends loosely through the turns of the coil. The mandrel preferably is made of wood, cylindrical in form, and has a metal supporting rod 4 extending through it axially. At its right-hand end, as seen in the drawing, the rod. 4 is journalled in a suitable support 5. On its left-hand end, the rod 4 is provided with a flattened portion 6 secured to which, by means of a clamping bolt and wing nut l, is a handle 8.

At the beginning of the insulating operation,

the edgewise wound coil is placed on the mandrel 3, the handle 8 being positioned, after loosening the nut I, substantially lengthwise of the mandrel to permit the coil to be easily slipped over the handle onto the mandrel. Then the handle is moved back to its transverse position with respect to the mandrel, shown in the drawing, and secured by tightening the nut 1. It will be understood that the turns of the coil as wound are preferably close together. One end of the coil, such as the right-hand end, is then secured to a transversely extending member 9 on the mandrel as by means of a pin l0 secured to the member 9 and extending through a hole in the end of the strip forming the coil. Suitable means, such as a nut I l, is provided to hold the end of the strip on the pin III. Then the operator stretches the coil axially and secures its other, or left-hand, end in the same way to a pin l2 secured to the handle 8. The coil is thus stretched out with its turns separated a substantial distance, such as one inch. This separation of the turns, of course, will depend upon the radial dimension of the strip conductor, and, in any case, it is suflicient to provide for the free application of the strip of paper insulation.

As shown in Fig. 2, the strip of crepe paper I is formed from a relatively wide strip cut crosswise of the corrugations or wrinkles of the paper, which strip is folded lengthwise somewhat on one side of its middle, and then wound up on the reel l3. First, the end of the paper strip I is applied to one end of the coil with its side portions on opposite sides of the coil and its bend or fold on the outer periphery of the strip conductor and suitably bound by a cord, as indicated by the reference numeral 14'. Then the operator grasps the handle 8 and turns the mandrel and coil counterclockwise with one hand while with his other hand, as indicated by reference numeral l5, he feeds the strip to the helical turn of the coil as the coil is rotated. At the same time, the operator grasps the strip tightly enough to apply a substantial tension to the strip as it is drawn through the fingers of the operator, whereby the paper strip is stretched so that its side portions lie substantially fiatwise against the sides of the strip conductor.

It will be understood that the paper strip is stretched the greatest amount at its bend or fold lying against the outer periphery of the turns of the coil, the stretching decreasing radially inward. Actually, the tension applied to the paper strip is not suflicient to stretch it throughout its entire width, the axially innermost edge being h loose or rufied somewhat. The tension is sulficient, however, to cause the folded portions to fit smoothly on the strip conductor over a substantial portion of its radius beginning from its outer peripheral edge, as indicated in Fig. 3.

also, at least one of the paper side portions in, as shown in Fig. 3, has a greater radial dimension than the strip conductor i6 so that its edge ll projects slightly beyond the inner edge of the strip conductor. This assures the effective electric insulation from each other of the. inner edges of the turns of conductor I6. While the coil is on the mandrel, this inner projecting edge it or the paper will lie against the mandrel and perhaps be bent toward the adjacent turn by engagement with the mandrel. When the coil is removed, however, from the mandrel, the inner edges ill straighten out.

The opposite or left-hand side portion of the paper strip, as seen in Figs. 2 and 3, is shorter than the side portion in so as to leave uncov= cred the lower left-hand side of the conductor it. This provides space for the lower thicker edge of the conductor, 1. e., the radially inner edge of the conductor, which was upset and thereby appreciably thickened during the forming operation, so that the length of the coil is substantially the same at the outer and inner edges of the turns.

When the turns of the coil have been thus completely covered with the paper insulation, the paper strip is cut off and secured to the opposite left-hand end, as indicated by the ref= erence numeral H8 in Fig. 4. Then the coil is removed from the mandrel by following the re= verse of the procedure described in connection with its mounting on the mandrel, as will be understood clearly from the preceding description.

After removal from the mandrel, the coil is preferably placed in a press and a very substantial pressure applied, thereby to compress the turns together and straighten any turns that may have been warped during the edgewise winding of the conductor strip. Then the coil is removed from the press and the turns are bound tightly together, while being held together by suitable clamping means. by wrapping several turns of cord [9 around the turns at spaced intervals, the cord extending axially through the coil, whereby the turns are secured tightly together. The last step in the formation of the coil is the impregnation of the crepe paper insulation with a suitable liquid electrically insulating varnish, such as a phenolic condensation product. The liquid insulating material preferably is forced thoroughly into the paper between the turns ofthe coil by applying it under pressure, as by immersing the ill its radially outer edge, and a layer or electric insulating material on said conductor consisting of a continuous strip of crepe paper impreg= nailed with an electrically insulating material, said paper strip having crosswise corrugations and extending lengthwise of said conductor with side portions on opposite sides of said conductor joined by a bend on the outer peripheral edge of said conductor, and said paper strip being stretched at its bend so thatisaid side portions lie substantially fiat on the sides of said conductor and one of said side portions being radially shorter than said conductor to provide space for said thicker inner edge of said conductor.

2. A coil for electric apparatus comprising a strip electric conductor wound edgewise into a helix, and a layer of electric insulating material on said conductor consisting of a strip of crepe paper impregnated with an electrically insulating material, said paper strip extending lengthwise of said conductor and having crosswise extending corrugations with side portions onopposite sidw of said conductor joined by a bend on the outer peripheral edge of said conductor and stretched at its bend so that its side portions lie substan-= tially flat on the side oi said conductor, at least one of said side portions of said paper'strip coils in the insulating material in a sealed container to which suitable air pressure is applied.

Thereafter, the coils are removed and the insulating material allowed to harden, preferably with the application of heat.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and Itherefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A coil for electric apparatus comprising a strip electric conductor wound edgewise into a being radially longer than said conductor so as to project beyond the inner edge of said con ductor thereby to insulate electrically the inner edges of said turns.

3. A coil for electric apparatus comprising a strip elecwic conductor wound edgewlse into a, helix with its radially inner edge thicker than its outer edge as a result of the winding operation, and a layer of electric insulating material on said conductor consisting of a continuous strip of crepe paper impregnated with an electrically in sulating material, said paper strip extending lengthwise of said conductor and'having cross? wise extending corrugations with side j-portiom on opposite sides of said conductor -joined by a bend on the outer peripheral edge of said conductcr and stretched at its bend so that its side:

portions lie substantially flat on the side of said conductor, one of said side portions or said paper strip being radially shorter than the said cong' ductor to provide space for said =thicker inn edge of said conductor and the other of sat side portions being radially longer than said 'conductorso as to project beyondthe inner edge of said conductor thereby to insulate the inner edges of said turns. g Y

4. A coil for electricapparatus comprising a; strip electric conductor formed edgewise into turns to form a helix, said conductor having a width appreciably greater'than its thickness and having its inner edge thicker than its outer edge as a result of the winding operation, and-a lazy I of electric insulating material on said-conduct 1 consisting of a length of crepe paper crosswise corrugations and an eccentric length;- wise fold therein, said paper overlying the outmperipheral edge of said conductor with side portions of unequal radial length on opposite sides of said conductor throughout the length of said conductor and between said turns of said conductor.

5. A coil for electric apparatus comprising a strip electric conductor wound edgewise into turns to form a helix, said conductor having a width appreciably greater than its thickness, a layer of electric insulating material on. said conelectrically ductor consisting of a continuous strip of crepe helix with its radially inner edge thicker than 5 p per having cr sswise corrugations. Said D 9 having an eccentric lengthwise fold therein overlying the outer peripheral edge of said conductor with sideportions of unequal length on opposite sides of said conductor throughout the length of said conductor and between the turns of said conductor, and means for holding the turns of helix clamped together in flatwise relation, thereby to hold said paper firmly in place on said turns. 7

6. A coil for electric apparatus comprising a strip electric conductor having a relatively narrow thickness compared with its width and wound portion of lesser length on one turn providing space for the side portion of greater length on the next consecutive turn, and means for clamping the turns of said helix together in fiatwise clamping relation, thereby to hold said paper in place.

' HERMAN BRI'I'IEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 359,205 Curtis Mar. 8, 1887 753,461 Anderson Mar. 1, 1904 783,546 Rupley Feb. 28, 1905 986,291 Honold Mar. 7, 1911 1,595,838 Turner Aug. 10, 1926 v 2,007,047 Gibbs July 2, 1935 2,344,334 Vienneau Mar. 14, 1944 2,380,111 Kasten July 10, 1945 2,385,983

Hanes Oct. 2. 1945 

